pd_dt_1.py

from itertools import product
import pandas as pd
import numpy as np

col_names = ["Day", "Month", "Year"]

df = pd.DataFrame(list(product([10, 11, 12], [8, 9], [2018, 2019])),
                   columns=col_names)

df['data'] = np.random.randn(len(df))

df = df.sort_values(['Year', 'Month'], ascending=[True, True])

print(df)


"""
    Day  Month  Year      data
0    10      8  2018  1.685356
4    11      8  2018  0.441383
8    12      8  2018  1.276089
2    10      9  2018 -0.260338
6    11      9  2018  0.404769
10   12      9  2018 -0.359598
1    10      8  2019  0.145498
5    11      8  2019 -0.731463
9    12      8  2019 -1.451633
3    10      9  2019 -0.988294
7    11      9  2019 -0.687049
11   12      9  2019 -0.067432
"""